Solid-state power supply system for rotating anode x-ray tubes

ABSTRACT

A compact solid-state power supply system for rotating anode Xray tubes. The system includes an AC-to-DC solid state power converter which drives an inverter oscillator using silicon controlled rectifiers. The system provides means for operating the rotating X-ray tube anode at either low or high speeds with automatic braking when going from high speed to low speed. Means are also provided for automatically restarting the system in the event of paralysis of the inverter oscillator. Further, through the use of a novel programmed two-step driving signal, the desired operating speed is reached in a fraction of a second. The unit is compact and lightweight for optimum ease of installation.

United States Patent [151 3,641,408

Fiocca 1 Feb. 8, 1972 [54] SOLID-STATE POWER SUPPLY 3,474,320 10/1969Chandler ..318/227 X SYSTEM FOR ROTATING ANODE X- 3,482,157 12/1969Borden et a1. ..3l8/227 RAY TUBES Primary Examiner-Gene Z. Rubinson [72]Inventor: Louis L. Fiocca, c/o Advanced Instrument A"0mey A]ter, weiss &whitesd Development Inc. 1001 North 25th Ave., Melrose Park, Ill. 6016057 ABSTRACT [22] Filed: 1970 A compact solid-state power supply systemfor rotating anode [21] APPLNO; 66 X-ray tubes. The system includes anAC-to-DC solid state power converter which drives an inverter oscillatorusing silicon controlled rectiflers. The system provides means for [52]US. Cl ..3l8/227, 318/230, 318/231, operating the rotating X43), tubeanode at either low or high 5 1 um Cl H speeds with automatic brakingwhen going from high speed to a I o u I I I u u I u I l u u I I n I I eI I u e l e Q I n I I a u u I n u u- [58] Field of Search 318/138 ingthe system in the event of paralysis of the inverter oscillator.Further, through the use of a novel programmed two-step driving signal,the desired operating speed is reached in a frac- [56] Reerences CM tionof a second. The unit is compact and lightweight for op- UNITED STATESPATENTS timum ease of installation.

3,416,057 12/1968 Froyd et a1 ..3 18/231 X 18 Claims, 2 Drawing FiguresI H I4 I80 HzBrd. 7 IO 1 24 voc l5 r Logic Q inverter l I powerOscillator D I m Comm 5U I 8rAmpl|f|er 60 Hz 6 I pp y I InputTransformer I l6 J 1 I80 Hz. I II 7 IQ [8 I Phase Shift I NeIwork AC toDC Automat|c SCR f3 J Conversion Start |nv n T I 24 V DC 60 H 5 d LogicPower 0.8 Sec. 23 I Supply Timer I V -27 1 20 I Sinusoidal I 60 Hz. r IFilter I Proqromminw Phase Shift 2 5 I lnput Relay Network l Logic I l IL I I I 24 M L m I 60 Hz Selection 22 Rotor Relays Smor Relay aSSplitPhase-o 0rd Command l 30R Bridge Contactor Capacitor S 19 no s I JSOLID-STATE POWER SUPPLY SYSTEM FOR ROTATING ANODE X-RAY TUBES Thisinvention relates to induction motor power supply systems, and moreparticularly to power supply systems for motor-driven rotary anodes ofX-ray tubes, or the like.

To provide for greatly increased ratings, X-ray tubes have long beenprovided with rotating anodes to increase the area of electronbombardment. Such anodes are generally driven with split phase motors,and in fact are the rotors of such motors. The motors are operated frompower sources capable of providing either 60-Hz. or lSOHz. AC controlpower to enable operation at anode rotation speeds of about 3,400 r.p.m.or 10,000 r.p.m., respectively. Such two-speed drive systems are greatlypreferred over single-speed drives, because the highspeed drive providesgreatly improved X-ray tube operating ratings and loadings.

To provide a source of 180 Hz. operating power, various systems havebeen employed. For example, originally motorgenerator sets were used,but these are bulky, noisy and inefficient. More recent systems usethyratron power oscillators driven by a full-wave rectifier operatingoff the alternating current power supply means through an isolatingtransformer. While this eliminates the use of rotating machinery otherthan the anode drive motor itself, such drive systems are nonethelessundesirably inefficient and bulky. Moreover, in addition to the frequentneed for thyratron replacement, the thyratron power oscillators in suchsystems are extremely susceptible to paralysis" caused by current spikeson starting despite the use of thyratrons with exceptionally highback-voltage ratings. It is necessary to provide a circuit breaker toshut the system off in the event of such paralysis. Restarting is thenmanually accomplished.

In addition, the prior art systems presently available acceleraterelatively slowly in attaining the final operating speed for the X-raytube anode in the high speed (180 Hz.) operating mode. In general, therotating anode and its motor drive exhibit mechanical resonances atspeeds in the range from 4,000 to 5,000 r.p.m., and it is highlydesirable to make the transition through such resonances, both onaccelerating and decelerating of the anode as brief as possible tominimize bearing wear of the rotating anode system and to minimize unduestrain on the glass envelope and bearing mounts, an thus improve X-raytube life. In addition, the brief transition through the resonancesmakes the entire system less noisey.

Accordingly, it is an object of the present invention to providesolid-state power supply systems for rotating X-ray tube anode, or thelike, which avoids one or more of the aforementioned disadvantages ofprior art systems.

It is a further object of the invention to provide a compact andrelatively lightweight solid-state power supply system for use withrotating anode X-ray tubes or as a supply for any inductive motor wherethe requirements include greatly reduced starting time as compared withprior art systems.

Yet another object of the invention is to provide a compact solid-statepower supply system for rotating anode X-ray tubes which provide foroperation at a low speed and at a high speed with greatly reducedsusceptibility to power oscillator paralysis and with automaticrestarting in the event of power oscillator paralysis.

A still further object of the invention is to provide relatively quietrotating anode X-ray tube systems.

In accordance with an exemplary embodiment of the invention, therotating anode power supply system comprises a solid-state source ofline frequency power and a source of power having a multiple of linefrequency. Each power source has means for providing either a normalrunning voltage or a higher boost voltage. The boost voltage is used toaccelerate the anode to obtain the desired speed of rotation in theshortest possible time. The anode is also automatically braked to reducethe run down time when power is removed from the anode motor or whenspeed is reduced. The multiple line frequency power source includes anSCR inverter that is provided with an automatic start facility in theevent of inverter paralysis. The system further is almost completelyautomatic, for example, it includes a short time timer and a long timetimer for use in controlling the time lengths of the boost voltage.

The above mentioned and other objects and features of the presentinvention which are believed to be novel are set forth withparticularity in the appended claims. The invention, together withfurther objects and advantages thereof, may best be understood byreference to the following description taken in connection with theaccompanying drawings, in the several figures of which like referencenumerals identify like elements, and in which:

FIG. I is a block diagram of a solid-state power supply system, whichembodies the present invention for the drive motor of a rotating anodeX-ray tube; and

FIG. 2 is a detailed schematic circuit diagram of the power supplysystem of FIG. 1 embodying the invention.

In FIG. I, a supply voltage, such as a 240 volt AC 60 Hz. input voltage,which may be derived from a commercial main power supply, is applied toa control transformer 10. The control transformer 10 supplies operatingcurrent to two subassemblies used to provide the line frequency powerand the multiple line frequency power. The subassemblies are shown as aHz. board 12 and a 60 Hz. board 13. Each subassembly is shown includinga power supply 11, actually as seen in FIG. 2, this may represent aplurality of power supplies. It should be understood that even thoughspecified frequencies are discussed herein, the system is not limited tosuch specified frequencies.

In the 180 Hz. board 12, power supply 11 powers means for providinghigher frequency power, such as a 180 Hz. oscillator and amplifier 14which in turn actuates an inverter-driver 15 to generate a square wavecontrol signal ultimately used to drive the rotating motor at the highspeed rate.

Means are provided in the multiple line frequency power supplysubassembly for controlling the current for enabling operation either ata boosted voltage condition, or at a run voltage condition. Moreparticularly, another 60 Hz. output voltage from control transformer 10is directed through a 180 Hz. phase shift network 16 to an externallymounted AC-to- DC conversion unit 17. The amplitude of the output signalfrom unit 17 is a function of the phase shift of network 16.

Means are provided for automatically controlling the amount of phaseshift, and consequently determining whether the supply is in the boostor run mode.

More particularly, programming and timing means are connected tocircuits l6 and 17. For example, the AC-to-DC conversion unit 17includes a DC power supply for developing a programmed DC driving signalfor application to an SCR (silicon-controlled rectifier) inverter 18.

Means are provided for automatically restarting the system, such as anautomatic start circuit 19, in the event a transient spike extinguishesthe inverter 18. The AC-to-DC conversion unit 17 also is connected toreceive a 240-volt AC 60 Hz. input from the main powerline.

On the 60 Hz. board 13, there is similarly means for enabling operationat either run" or boost" power conditions, such as a 60 Hz. phase shiftnetwork 20. Actually, the phase shift network determines whether thesystem is in the quiescent condition, run condition or boost condition.The network 20 shifts a 60 Hz. input signal to provide a phase shiftedoutput signal from control transformer 10 to a 60 Hz. SCR(silicon-controlled rectifier) bridge circuit 21. The output signalamplitude of the bridge circuit 21 is a function of the amount of phaseshift provided to the circuit 21.

Means, such as selection relay contactor unit 22, are provided forselecting either the regular rotational speed drive or the higherrotational speed drive. Selection relay contactor unit 22 receives boththe sine wave component of the output signal from SCR inverter 18,applied thereto by means of a sinusoidal filter 23 and the output ofbridge circuit 21. The selection relay contactor unit 22 in turn iscoupled through the rotor relay circuits and split phase capacitornetwork to the stator cord terminal which is adapted to be connected tothe stator circuit of the drive motor for the rotating anode of theassociated Xuray tube (not shown).

Means are provided for automatically timing the boost condition of saidsubassemblies. In greater detail, board 13 also includes a pair oftimers There is a short-time (0.8 second for example) timer 25 which ispowered by DC logic power supply 11 and is coupled to phase shiftnetworks 16 and 20, and a long-time (2 second, for example) timer 26,also powered by power supply 11, which is coupled only to a 60 Hz. phaseshift network 20. The 60 Hz. shift network 20 controls the outputamplitude of a 60 Hz. SCR bridge network 21, which is powered by a 240volt AC 60 Hz. input from the main power supply. Board 13 is alsoprovided with programming input relay logic circuitry 27 which, asindicated by the legend, responds to input command signals and controlsphase shift networks 16 and 20 and timers 25 and 26.

In operation, the 240 volt AC 60 Hz. input voltage applied to controltransformer supplies the 24 volt DC logic power supply 11, the'180 Hz.phase shift network 16, and the 60 Hz. phase shift network 20 withappropriate 60 Hz. input voltages. Power supply 11 generates DC outputvoltages of approximately 24 volts whichare employed to supply the 180Hz. oscillator and amplifier 14, the timers 25 and 26, and the 60 Hz.phase shift network 20 with appropriate operating voltages.

Means are provided for supplying the anode motor with high-speedsynchronous driving power. For example, unit 14 develops a 180 Hz.output signal which is supplied through inverter driver 15 to SCRinverter 18 to develop a 180 Hz. square wave output signal. A sinusoidalfilter 23 derives the fundamental component of the square wave outputfrom SCR inverter 18 to deliver a sine wave 180 Hz. output signal toselection relay contactor unit 22 and thence, when the system is in the180 Hz. operating mode, through rotor relays and split phase capacitorunit 24 to the stator terminals of the drive motor for the X-ray anodetube.

The AC-to-DC conversion unit 17 receives a 240 volt AC 60 Hz. inputvoltage from the main power supply and is controlled by programminginput relay logic system 27 through 180 Hz. phase shift network 16 todeliver the programmed two-step input voltage through automatic startunit 19 to SCR inverter 18.

The short time timer unit 25 is employed in the ISO I-Iz. mode tocontrol phase shift network 16 in connection with the programming of thetwo-step input voltage for SCR inverter 18.

In the 60 Hz. operating mode, programming input relay logic system 27controls the 60 Hz. phase shift network 20, in conjunction with the longtime timer 26 and the short time timer 25, to turn on the 60 Hz. SCRbridge 21 which is supplied from the main power supply with a 240 volt60 Hz. AC input signal voltage. The output from SCR bridge 21 is appliedto selection relay contactor unit 22, and in the 60 Hz. operating mode,this voltage is applied through rotor relays and split phase capacitorunit 24 to the input terminals of the X-ray drive motor stator.

The construction and operation of the system can be appreciated ingreater detail from the detailed schematic circuit diagram of FIG. 2.This exemplary system uses transistors and relays which derive powerfrom 5 DC power supplies on two printed circuit board assemblies. Forconvenience, transistors are conventionally designated by Q numbers fromO1 to Q29, inclusive, while relays are designated with K/number (orK/letter) combinations. Contacts associated with each relay bear thesame K/number combination designations followed by a -No.; thus thefirst contact referred to of relay K1 is designated as contact Kl-l.Normally, open contacts are shown as a pair of spaced parallel plates,while normally closed contacts have a slanted crossline bridging thecontacts. Conventional symbols are used for each of the components andthe operation of the system will be described in detail by reference tothe several transistors and relays, respectively.

Input phase control means, such as network 16 including theresistance-capacitance network 30 are provided at the input of the 180Hz. board. The sinusoidal phase-shifted signal from theresistance-capacitance network 30 acts as the input to transistor Q1.When the normally open contacts K1-1 and Kz-l associated with phaseshift network 30 are both open, as in the quiescent state (idlecondition), nearly 180 of phase shift occurs so that the firing anglesof SCRI and SCR2 of AC- to-DC conversion unit 17 (FIG. I) are nearlyzero.

On closing of contacts Kl-l and [(2-1, the resistors bridging thesecontacts are shorted out and the resulting phase shift then approaches 0so that the firing angles of SCRI and SCR2 are such as to sustain nearly180 of conduction in each cycle. This is the boost condition, and willallow maximum current flow in the full-wave SCR bridge comprisingsilicon-controlled rectifiers SCRl and SCR2, charging the outputcapacitors 31 and 32 through a series air core choke coil 33.

The charge on capacitors 31 and 32 provides an increased DC voltage orthe boost condition. The boosted voltage constitutes the B+ supply forthe 180 Hz. SCR inverter section 18 (FIG. 1). In the run condition, onlycontact K1-l is closed while contact Kz-l is open, and this provides aphase shift of approximately 110 or a firing angle of in the bridgecircuit comprising SCRI and SCR2. The charge on capacitors 31 and 32 inthe run condition is a reduced DC voltage, and the inverter runs at thisreduced voltage level.

The base of transistor Q1 is tied to the phase shifted sinusoidal signalthrough coupling resistor 34 and a portion of the secondary of controltransformer 10. Resistor 36 provides biasing for the base of transistorQ1. The collector of transistor Q1 is connected to B+ through loadresistor 37 and the emitter is connected directly to B- as provided bypower supply 11.

The output of transistor O1 is a square wave which is coupled directlyto the base of transistor O2 to switch transistor Q2 which in turnswitches transistor Q3. Therefore, the outputs of transistors 02 and Q3are always 180 out of phase with each other. These output signals eachsupply 50 milliamperes 50 gate current drive to SCRI and SCR2,respectively.

It should be noted that the rest of the biasing, coupling and outputresistors will not be described hereinafter to preclude needlesslyburdening the description of the operation of the inventive supply.Table 1, however, is attached to give exemplary values of the componentsshown in the drawings.

Transistors Q4, Q5, Q6, Q7, Q8 and Q9 and their associated circuitcomponents constitute the 180 Hz. Oscillator and Amplifier unit 14 ofFIG. 1. Transistors Q4 and Q5 are connected in a conventionalmultivibrator oscillator circuit having a frequency of oscillation of360 Hz.

The signal output from the multivibrator comprising transistors Q4 andO5 is amplified and shaped with transistors Q6 and Q7. The output oftransistor Q7 is a square-wave with a sharp falling edge in order totrigger the flip-flop circuit comprising transistors Q8 and Q9. Theflip-flop circuit comprising transistors Q8 and Q9 divides the 360 Hz.operating frequency from the Q7 driver transistor by a factor of two toprovide an output signal between the collectors of transistors Q8 and Q9in the form of 180 Hz. square wave 50 percent duty cycle wave forms.

Transistors O10, O11, Q12 and Q13, and their associated circuitcomponents constitute the inverter driver circuit 15 of FIG. 1. Theoutputs of the flip-flop circuits comprising transistors Q8 and 09 aredifferentiated by the networks 79 and 90, and the differentiated pulsesare current-amplified by transistors O10, Q12 and Q11, Q13,respectively.

In an exemplary embodiment, transistors QI2 and Q13 supply milliampereseach to SCR3 and SCR4 of the Hz. SCR inverter unit (FIG. 1). Thesecurrent pulses of 100 milliamperes occur each 5.5 milliseconds and are2.75 milliseconds apart and have a pulse duration of 200 microseconds.

Silicon-controlled rectifiers, SCR3 and SCR4 are connected to provide afree-running inverter commutated by capacitor 49 in a conventionalMcMurray-Bedford inverter circuit, which drives into the primary windingof an inverter transformer 37.

Transistors O14, O15, Q16, Q18, Q20 and Q22 and their associated circuitcomponents constitute the programmed input relay logic system 27 of FIG.1.

When the 180 Hz. control (not shown) is actuated, relay K11 operates dueto the voltage applied between the positive voltage applied to terminal197 and 8- obtained from supply 11. Responsive thereto, contacts Kll-lin the input circuit to transistor Q14 closes, and relay K1 is activatedover the circuit extending from a 24v. source through the K1 relay coil,diode D1, contacts K11-1 to ground. The capacitor 60 in the inputcircuit between the base and the emitter of transistor Q14 charges fromthe 24 volt source through contacts Kl-2 and thereby causes a time delayof approximately 50 milliseconds before transistors Q14, Q15 and Q16change states. When the charge reaches approximately 3 volts, transistorQ14 becomes conductive and this in turn cuts off transistor Q15 whichtriggers transistor Q16 to the ON state. Relay K2 is now energizedthrough the circuit including transistor Q16, diode D1 and the normallyclosed contacts KT-l of timing relay K to ground. The operation ofrelays K1 and K2 now initiate the high-speed power boost condition whichaccelerates the motor to bring it up to synchronous speed in a fractionof the time required with other presently available equipment.

Timing relay contacts KT-l open after a delay that is determined by theshort time timer 25. The short time timer comprises transistors Q27, Q28and Q29. The operation of the timer circuit 25 will be explained furtherin the specification. Responsive to the opening of contacts KT-l, relayK2 drops out which places the 180 Hz. supply into the run condition. Thecircuit comprising transistors Q14, Q15 and 016 which control relay K2is the programmed input relay logic circuitry for the high-speedoperation.

The operation of transistors Q18, Q and Q22 in subassembly 13 is almostidentical to that of transistors Q14, Q15 and Q16. Relays K3 and K4determine the boost and run conditions for the 60 Hz. mode of operationresponsive to the operation of relay K10 in a manner analogous to relaysK1 and K2 in the high-speed operation condition.

ransistors O17, Q19 and Q21 and their associated circuit componentsconstitute the 60 Hz. phase shift network 20 of FIG. 1, and theiroperation is almost identical to that of transistors Q1, Q2 and Q3 ofthe 180 Hz. phase shift network 16 (FIG. 1). Transistors Q18 and Q21supply 50 milliamperes of gate signal through resistors 133 and 134,respectively, to the bridge circuit comprising silicon-controlledrectifiers SCRS and SCR6. This the 60 Hz. bridge circuit 21 and it iscoupled to a 2-to-1 stepdown transformer 42 as the controlled element.

The phase shift firing angle of the bridge circuit comprising SCRS andSCR6 is controlled so that in the 60 Hz. boost condition, transformer136 approaches a conduction angle of 360. In the 60 Hz. run cycle, theconduction angle is approximately 140. In this manner, the RMS voltageat the secondary side of transformer 136 is either 115 volts AC (boost),40 volts AC (run) or nearly zero (idle).

Transistors Q23, Q24, Q25 and Q26 and their associated circuit elementsconstitute the long time timer unit 26 of FIG. 1. When the 180 Hz. modeof operation is discontinued, relay K1 is deenergized and the +24 VDCterminal 183 is switched through the normally closed Kl-4 contacts intothe input circuits of transistors Q23 and 024. The capacitor 161 betweenbase and emitter of transistor Q23 acts as a slug; i.e., it chargesthrough resistor 157 for approximately one-half second until the voltageis sufficient to turn on transistor Q23 which in turn energizes brakingrelay K14. The energized braking relay applies a braking force to theanode through contacts K-l. When the normally open contacts K14-1 at thelower lefthand portion of the circuit diagram close, relay K3 isenergized. Responsive thereto, transistor Q18 switches to its conductivestate causing transistor Q20 to switch to its nonconductive state. Whentransistor Q20 is nonconductive, transistor Q21 is biased to conduct andthereby energize relay K4. Thus, relay K3 and K4 are energized, and thisnow initiates the 60 Hz. boost mode of operation, which acts to brakethe anode and drop it to the lower rotational speed in a shorter time.

The input capacitor 164 of transistor Q24 then charges through resistor46 for approximately 2.5 seconds until the voltage is sufficient to turnon transistor 024. When transistor Q24 becomes conductive, this causestransistor Q25 to become nonconductive and transistor Q26 to becomeconductive, and this causes the ground from terminal 186 to be appliedto the common side of the K14 relay coil thus causing relay K14 todeenergize and terminate the braking cycle.

Transistors O27, Q28 and Q29 and their associated circuit componentsconstitute the short time timer 25 of FIG. 1. When any of the normallyopen contacts of relays K10, K11, K12 or K13 are closed, then the +24VDC terminal 184 is applied to charge capacitor 176 through a resistor172 and a potentiometer 173 until the voltage is sufficient to maketransistor Q27 conductive. When transistor Q27 conducts transistor Q28turns off and makes transistor Q29 conductive to energize timing relayKT. This short boost time is factory calibrated by adjustment ofpotentiometer 173 to provide a total tum-on time for relay KT of 0.8second. The operation of relay KT opens contacts KT-l, KT-2 (aspreviously explained) to deenergize relay K1, K3, respectively andreturn the system to the run condition from the boost condition.

In operation, when the 60 cycle or 3,400 rpm. mode of operation isdesired, a voltage is applied through controls in the X-ray equipment(not shown) to apply 12 volts to terminal 202. The 12 volts thus appliedactuates relay K10 by extending the positive voltage through diode D19,the coil of relay K10, to negative voltage received from a portion ofpower supply 11.

Responsive to the energization of coil K10, contacts K101 operate toclose a path for operating relay coil K3 through a path that extendsfrom the negative voltage, through normally closed contacts K1l2,contacts K10-1, diode D12 and the coil of relay K3 to positive voltagereceived from a portion of power supply 1 1.

Another set of contacts of relay K10; namely, contacts K102 also closeto establish a circuit for operating the timing relay KT. The timingrelay KT, as previously explained, is in the short time timer circuits25 and operated to automatically limit the boost voltage operate times.Thus, the closure of the normally open relay contacts K10-2 applies 24volts that is on terminal 184 to charge capacitor 176 through thecircuit that extends from terminal 184 through relay contacts K10-2,resistor 172, potentiometer 173, and through capacitor 176 to ground onterminal 186. When the charge on capacitor 48 builds up sufficiently(0.8 sec. in an exemplary embodiment) to switch the normallynonconductive transistor Q27 to conduct and to turn off normallyconducting transistor Q28 to turn on normally nonconducting transistorQ29 and energize timing relay KT. During that 800 millisecond timeperiod required to operate relay KT, relay K3, of course, is operated.The operation of relay K3 closes a circuit that enables the operation ofrelay K4. More particularly, normally open contacts K32 close to extendpositive voltage from a portion of power supply 11 through contacts K32and resistor 147 to charge capacitor C6. The charging of capacitor C6delays the operation of switching transistor Q18 from its normallynonconducting state to its conducting state by a period of approximately50 milliseconds. As soon as it charges sufficiently, however, the biasis applied to the base of transistor Q18 through resistor 151 andbiasing resistor 152. Transistor Q18 in its conducting state causestransistor Q20 to switch from its conducting to its nonconducting state,and consequently to switch transistor Q22 to its conducting state toenergize relay coil K4 over the circuit that extends from positivevoltage of power supply 11 through transistor Q22, OR-gate diode D12, tonegative voltage. Contacts KT-2 remain normally closed since relay coilKT is not energized at this time because of the 800 millisecond delay.When relays K3 and K4 are both energized, contacts K3-1 and K4-1 closeto place the 60 Hz. subassembly in boost condition, as previouslyexplained. As soon as relay KT energized, then contacts KT-2 open todeenergize relay K4 and place the 60 Hz. subassembly into the runcondition.

When the signal is removed from the coil of relay K10, then contacts K-1return to the normal condition removing energization power from the coilof relay K3. Thus, both contacts [(3-1 and 1011-1 no longer short outresistors 121 and 123, respectively. At this point, the subassembly isin the idle condition.

lt should be noted that normally output stator power is supplied to thetransformer 136 of the 60 Hz. subassembly. The power extends from thebottom side of the secondary of transformer 136 through the closedcontacts KS-1 to terminal 190 and from the top side of the secondary oftransformer 36 through normally closed contact KS-2, the coil of relayK6 to terminal 189. The top sides of the secondary of transformer 136 isalso tied to terminal 188 through capacitors 137 and 138 in parallel andthe coil of relay K5.

The 180 Hz. operation is similar in many respects to the 60 Hz.operation. When a positive voltage is applied to terminal 197 in anywell known manner, then relay K11 is energized over a circuit thatextends from the positive voltage through diode D17 through the coil ofrelay K11 to negative voltage received from a portion of power supply11.

The operation of relay K11 enables the operation of relay Kl over acircuit that extends from positive voltage, through the coil of relayK1, diode D7, the now closed normally open contacts K1 l-l to ground.The energization of the coil of relay K1, of course, closes contactsKl-l to short out resistor 51 and vary the phase of the output of the180 phase shift network. At the same time, contacts K1-2 also close tostart a programming input relay logic operation. More particularly,normally nonconducting transistor Q14 is caused to conduct aftercapacitor 60 builds up sufficient charge. In an exemplary embodiment ofthe invention, this takes about 50 milliseconds. Coupling resistor 59couples the base of transistor Q14 and resistor 61 biases that base toswitch the normally nonconducting transistor Q14 to the conductingstage. Responsive thereto, transistor Q15 is switched from the normallyconducting stage to the nonconducting stage. it should be noted that thebase of transistor Q15 is directly coupled to the bias resistor 62 oftransistor Q14. Similarly, normally nonconducting transistor Q16 isswitched to the conducting stage because the base of transistor Q16 istied to the junction point of load resistor 63, and the collector oftransistor Q15 when transistor Q15 switches and energizes the coil ofrelay K2.

The energization circuit extends from positive voltage through the coilof relay K2, transistor Q16, diode D6, closed contacts KT-l of timingrelay KT, diode D7 to negative voltage.

The operation of relay K2 closes a normally open contact K2-1 to furthervary the phase of the output signals of the 180 Hz. phase shift network.This maximizes the voltage output of circuit 17, as previouslydescribed, so that the 180 Hz. subassembly is operating in the boostcondition.

The boost condition lasts until relay KT is energized as explained withreference to the 60 Hz. subassembly. The operation of relay KT openscontacts KT-1 to remove the operating circuit for relay K2. When onlyrelay K1 is operated, then the phase shift of the I80 Hz. phase shiftcircuit is such as to provide a run voltage condition.

It should be noted that a discharge circuit is provided for bothcapacitors 60 and 149 through contacts K14 1(2-3 and K3-3, K4-3,respectively. This run down circuit functions when the circuit is turnedoff.

The operation of the timing relay KT is the 180 Hz. mode is initiated bythe operation of relay K11 through contacts K11-2 instead of contactsK1114...

Means are provided for assuring that the output to the stator isprovided by the Hz. circuit instead of by the 60 Hz. circuit. Moreparticularly, relay KS is operated responsive to the operation of relayK11 over circuit that extends from positive voltage of terminal 184through contacts K11-2, diode D23 and the coil of relay KS to'ground.The actual operation of relay KS is delayed by the series circuitcomprising resistor 181 and capacitor 182. It should be noted that whencontacts K10-2 operate, diode D23 prevents the consequent operation ofrelay KS.

Responsive to the operation of relay KS, contacts KS1 open to disconnecttransformer 136 from the output stator cord circuit. Contacts KS-Z opento remove capacitor 137 from the circuit and contacts KS-3 close toconnect the sinusoidal filter comprising inductor 139 and capacitors 141and 1412 in series with terminals 189 and 190, respectively. At thistime, capacitor 137 is no longer in the circuit. Capacitor 138 isbridged across terminals and 196.

Means are also provided for braking the rotor to slow it down wheneither stopping or changing from the high speed to the normal condition.More particularly, braking relay K14 is provided. Relay K14 operatesresponsive to a circuit that extends from positive voltage at terminal183 through contacts K14, normally closed, resistor 158 to the top sideof the coil of braking relay K14. The bottom side of the coil of brakingrelay K141 is connected to the collector of transistor Q23.

it should be noted that transistor Q23 goes from the normallynonconducting condition to the conducting condition responsive to thepositive voltage received through contacts K14l and resistor 157 whichcharges capacitor 161 in approximately 20 seconds. Thus, the brakingrelay is actuated twenty seconds after relay K1 returns to normal.

It also should be noted that the relay K1 release time is affected bythe presence of resistor 58 in series with the parallel capacitors 104and 110. These capacitors discharge through resistor 58 and the coil ofrelay K1 to cause relay K1 to be slow to release.

The switching of transistor Q23 energizes the braking relay K14. Thebraking relay causes braking power to be transmitted to the anode tobrake it. in greater detail, responsive to the energization of relayK14, contacts K14l close in the 60 cycle subassembly and provide anoperating circuit for relay K3 in parallel to the previously discussedoperating circuit utilizing contacts K10-1. Thus, the time of operationof the the high-speed circuit is limited by the braking relay. In otherwords, as soon as the braking relay operates, then relay K3 operateswith its subsequent operation of relay K4. The operation of the brakingcircuit is initiated by the removal of the positive voltage from theinput to K11. The operation of relay K10 is caused by the application ofpower thereto which may be responsive to the operation of the brakingrelay K14. Thus, the power from transformer 137 is switched to theoutput instead of the power of transformer 48. Accordingly,approximately 800 milliseconds after the initiation of the ISO Hz. orhigh-speed mode of operation, boost voltage is removed, and run" voltageis supplied. Within approximately 20 seconds after the initiation of thehigh-speed mode, braking power is applied and the low-speed mode iseither automatically or manually initiated. Upon going to the low-speedmode, a boost condition is initiated and braking is applied forapproximately 2 seconds under the control of timing circuit 26. At theend of the two seconds, Q26 switches to the conducting condition todeenergize braking relay K41 as has previously been described.

Means are provided for operation on the low-speed mode responsive toactuation of a fluoroscope switch. More particularly, relay K12 isenergized by the operation of a fluoroscope switch that applies positivevoltage to terminal 198 through the coil of relay K12 to ground atterminal 199. The operation of relay K12 closes contacts K12-1 to applypositive voltage from power supply 11 through resistor 156, normallyclosed contacts K134, contacts K12-1, the coil of relay K10 to negativevoltage from power supply 11. The previously described operation of the60 Hz. mode is thus automatically placed into effect.

Similarly, means are provided for high-speed operation responsive to theactuation of a spot film switch to enable filming from the fluoroscopemode. Positive voltage is applied to terminal 201 through the coil ofrelay K13 to ground at terminal 199. The operation of relay K13 thenopens contacts K13-1 and closes contact K13-2. The closing of contactsK13-2 enables relay K11 to be energized over the circuit extending frompositive voltage through resistor 156, closed contacts 1413-2, diode D16and through the coil of relay K11 to negative voltage supply from powersupply 11.

The operation of contacts K13-1 to the open position keeps relay K fromoperating.

It should be noted that series contacts K10-3 and K1 14 are provided forbleeding capacitor 176 when neither of those relays are operated.

Means are provided for automatically restarting the inverter in theevent of the SCR inverter 17 is upset, as for example, by a transient.In that case, both SCR3 and SCR4 would be in a steady-state conditionand would present a short-circuit condition to the 13+ supply. The 13+supply would then collapse and consequently relay K9 would bedeenergized to open contacts K9-l and remove the b+ from the inverter.Consequently, SCR3 and the SCR4 would turn off and return to the normalfree running mode; thereby, removing the short circuit and K9 wouldagain be energized. Thus, the paralysis condition is automaticallycorrected by means such as mode monitoring relay K9.

Means are provided for monitoring the stator cord circuit to determinewhether or not boost current is being delivered into the stator of theX-ray tube. More particularly, current relays K5 and K6 appear in serieswith terminals 188 and 189, respectively. Relay K7 is a voltage relayplaced across a split phase start capacitor. 1t monitors the capacitorvoltage in the boost condition.

K8 is a slave relay that operates responsive to the operation ofcontacts K5-1, 1(6-1 and K7-1, which occurs only in the boost condition.when relay K8 is energized, contacts K8-1 close to lock it in.

The relays discussed also may be used to control various operations ofthe X-ray equipment. For example, the operation of relay K8 indicatesthe boost condition, and contacts K8-2 energizes a filament boostcircuit. Also, the series circuit of contacts KT-3 and K8-3 provides aninterlock circuit.

The circuitry described is equipped with various devices for precludingadverse effects due to inductive kickback. For example, the invertercircuit utilizes flyback diodes such as diodes D3, D4. Also, thyrectorsT1, T2 are used.

Thus, the circuitry presented automatically provides a highand alow-speed operating mode. Braking is applied between the highspeed andthe low-speed modes. Boost and run voltages are supplied for each mode.The switching is almost all automatically accomplished, and theoperation is relatively quiet.

While the principles of the invention have been described above inconnection with specific apparatus, it is to be clearly understood thatthis description is made only by way of example and not as a limitationon the scope of the invention.

TABLE 1 60 Hz. FREQUENCY CONTROL (A-2) 126 10K 1wv 127 10K ll2w. 1282.2K 1/2w. 129 220 ohm 1w. 131 1.2K 1/2wr 132 220 ohm 1w. 133 220 ohm1w, 134 220 ohm 1w.

143 470 ohm 1/2w. 147 22K 1/2wv 14B ohm l/2w. 151 10K 1/2w. 152 10K1/2wr 1S3 10K 1/2w. 154 [K 1/2w. 156 22K 1/2w. 157 1K l/Zw. 158 ohm 5wv159 113K 1/2w. 163 47K 1/2w, 165 470K ll2w. 166 39K 1/Zw. 167 22K 1I2w.168 39K 1/2w. 169 2.7K l/2w. 171 100K l/2w. 172 33K 1/2w. 173 100K(Potentiometer) 174 22K l/2w. 177 22K 1/2w. 178 22K 1/2wr 179 2.2K 1/2w.181 270K l/2w.

CAPACITORS 124 Zmfd. ZOOVDC 125 640mm. 25VDC 144 10mt'd. 25VDC 146lornfd. ZSVDC 149 25mfd. 25VDC 161 100mm. 40VDC 164 200mfd. ZSVDC 176100mt'd. 40VDC 182 100mm. 40VDC TABLE 11 Hz. FREQUENCY CONTROL (A-l)RESISTORS Reference Numbers Component Value 10K 2.2K 220 ohm 2.2K 220ohm 220 ohm 210 ohm 22K 39K 3.9K 1K 76 IX l/ZW. 77 3.9K l/2w. 78 3.9Kl/Zw. 8i 10K l/2w. 82 10K l/Zw. 83 5.6K l/2w. 4 IX l/2w. 86 200 ohm 3 w.

88 5.6K l/Zw. 89 5.6K l/2w. 92 IX l/Zw. 93 3.9K l/2w. 94 3.9K l/Zw. 9610K ll2w. 98 10K l/Zw. 99 5.6K l/Zw. ll lK 112w. I02 200 ohm 3w.

I03 100K ll2w. I 5.6K l/2w. 108 5.6K l/2w.

TRANSISTORS I claim:

1. An induction motor supply system such as used for powering rotatinganode X-ray tubes, wherein the X-ray tube anode is either driven by themotor rotor or is the motor rotor,

said power supply system comprising a first solid-state power source forsupplying normal power required for driving the rotor of said motor at afirst running speed, a second solid-state power source for supplyingnormal power required for driving the rotor of said motor at a secondrunning speed,

said second speed being higher than said first speed,

boost means for increasing the power to the motor for a predeterminedperiod of time above the normal running power to accelerate the rotorwhile attaining said first and second running speeds,

means for decreasing said power to the normal running power after saidpredetermined period of time, and

means for selectively connecting the stator of said motor to either saidfirst or said second power sources.

2. The power supply system of claim 1 wherein boost timing means areprovided for automatically limiting the operating time of said boostmeans.

3. The power supply of claim 1 wherein means are provided for monitoringsaid boost means to ascertain operation thereof.

4. The power supply system of claim 1 wherein said first solid-statepower source means comprises control transformer means for coupling to apower line to provide low voltage at line frequency,

means for coupling said line frequency signal from the secondary of saidcontrol transformer to first solid-state phase shift means,

said last-named phase shift means for phase shifting said linefrequency,

means using the phase shifted line frequency to control asilicon-controlled rectifier bridge circuit so that the firing angles ofthe two silicon controlled rectifiers of the bridge circuit provide aboost power output from said bridge circuit and a running power outputfrom said bridge circuit by varying the phase shift of said linefrequency phase shift network means, and

means for selectively connecting the output of said silicon controlledrectifier to the stator of said induction motor.

5. The power supply system of claim 4 including timing means forlimiting the time of the phase shift resulting in the boost power tothereby automatically vary the phase shift after a first timer period.

6. An induction motor power supply system such as used for rotating theanode of X-ray tubes, wherein the X-ray tube anode is either driven bythe rotor of the induction motor or is the induction motor rotor,

said power supply system comprising a first solid state power source forsupplying normal power required for driving the rotor of said motor at afirst running speed, a second solid state power source for supplyingnormal 5 power for driving the rotor of said motor at a second runningspeed, said second speed being higher than said first speed, boost meansfor increasing the power to the motor for a predetermined period of timeabove the normal running power to accelerate the motor while attainingsaid first and second running speeds,

means for decreasing said power to the normal running power after saidpredetermined period of time,

I 5 means for selectively connecting the stator of said motor to eithersaid first or said second power sources, and

braking means for braking said motor when switching from said secondspeed.

7. The power supply system of claim 6 wherein braking timing means areprovided for automatically limiting the operating time of said brakingmeans.

8. The power supply system of claim 6 wherein said braking meanscomprises a braking relay,

means for operating said braking relay responsive to switching off saidsecond solid-state power source,

means responsive to the operation of said braking means fordeaccelerating the speed of the anode from said second speed to saidfirst speed, and

said last-named means comprising means responsive to the operation ofthe braking relay for operating said first solid-state power source at aboost power condition.

9. The power supply means of claim 8 wherein means are providedautomatically time limiting the operating period of said braking relay,whereby said second power source is returned to the running powercondition from the boost power condition at the end of a defined timeperiod.

10. An induction motor power supply system such as used for powering therotating anode of X-ray tubes, wherein the X-ray tube anode is eitherdriven by the motor rotor or is the motor rotor,

said power supply system comprising a first solid-state power source fordriving the rotor of said motor at a first running speed, a secondsolid-state power source for driving the rotor of said motor at a secondspeed,

said second speed being higher than said first speed,

boost means for accelerating the rotor to said first and second speeds,

means for selectively connecting the stator of said motor to either saidfirst or said second power source,

control transformer means for coupling to a power line to provide linefrequency power,

AC-to-DC power supply means coupled to the secondary of said controltransformer for supplying direct current power,

oscillator means powered from said direct current power for providing asignal having a frequency greater than the line frequency,

inverter means driven by said oscillator means to provide a drivingpower at a frequency higher than line frequency for driving the saidrotor, and

means for automatically restarting said inverter is said inverter isextinguished.

11. The power supply system of claim 10 wherein said in- 65 vertercomprises a silicon-controlled rectifier inverter having a first and asecond SCR,

said first and second SCRs normally operating individually,

said oscillator means including inverter driver means having a pair ofoutputs,

each of said outputs being individually coupled to one of the gates ofsaid SCRs alternatively gating said silicon-controlled rectifiers,

AC-to-DC converter means coupled to said line power, the

output of said AC-to-DC converter means being connected across saidfirst and second SCRs, and

said means for restarting said inverter comprising restarting relay coilmeans connected across the output of said AC- to-DC converter means tokeep said restarting relay energized unless both SCRs are gatedsimultaneously,

restarting normally open relay contact means in series with the outputof said AC-to-DC converter means for decoupling said AC-to-DC convertermeans from said silicon'conu'olled rectifier inverter in the event bothof said silicon-controlled rectifiers are gated simultaneously, therebyremoving power from the silicon-controlled rectifier inverter means andautomatically reenergizing said restarting relay to reconnect saidinverter means to said AGto-DC converter means.

12. The induction motor power supply system of claim 11 wherein saidboost means comprises means individual to said second solid-state powersource for providing a boosted power output from said second solid-statepower source for accelerating the anode so that it reaches the secondspeed in a relatively small time period.

13. The power supply system of claim 12 wherein the AC- to-DC convertermeans comprises a pair of silicon-controlled rectifiers, and wherein theboost means individual to said second solid-state power source comprisesphase shift network means coupled to the secondary of said controltransformer,

the output of said phase shift network being coupled to said AC-to-DCconverter means for determining the firing angles of the siliconcontrolled rectifiers in said AC-to-DC converter means and therebydetermining the power output from said AC-to-DC converter means.

14. The power supply system of claim 13 including timing means forautomatically changing the phase shift after a first period of time toreduce the boosted power to normal running power.

15. An induction motor power supply system such as used for rotating theanode of X-ray tubes, wherein the X-ray tube anode is either driven bythe motor rotor or is the motor rotor,

said power supply system comprising a first solid-state power source fordriving the rotor of said motor at a first speed, a second solid-statepower source for driving the rotor of said motor at a second speed,

said second speed being higher than said first speed,

boost means for accelerating the rotor to said first and second speeds,

second solid-state power source switching means for initiating theoperation of said second solid-state power source, means for selectivelyconnecting the stator of said motor to either said first or said secondpower source comprising selection switching means operated responsive tothe operation of second solid-state switching means, and

means responsive to the operation of said selection switching means forswitching the coupling of the stator of the induction motor from theoutput of said first solidstate power source to the output of saidsecond solid-state power source.

16. The power supply system of claim 15 wherein said selection switchingmeans comprises a selection relay, and wherein said second solid-statepower source switching means comprises a second solid-state power sourcerelay means,

normally open contacts on said second solid-state power source relaymeans operating to complete an operating circuit for said selectionrelay.

17. The power supply system of claim 16 wherein split phase startcapacitor means are provided for said induction motor,

said split phase capacitor means comprising a first and a secondcapacitor,

means including contacts on said selection relay for connecting saidfirst and second capacitors in parallel when said first power source isconnected to the stator of said motor, means including contacts on saidswitching relay for disconnecting said first capacitor responsive tosaid second solid-state power source being coupled to the stator of saidinduction motor.

18. An induction motor supply system such as used for powering X-raytubes having rotating anodes, wherein the X- ray tube anode is eitherdriven by the motor rotor or is the motor rotor,

said power supply system comprising a first solid-state power source fordriving the motor of said rotor at a first speed, a second solid-statepower source for driving the rotor of said motor at a second speed, saidsecond speed being higher than said first running speed,

boost means for increasing the power to the motor above the normalrunning power to accelerate the rotor while obtaining the first andsecond running speeds,

means for selectively connecting the stator of said motor to either saidfirst or said second power sources, and

means for monitoring said boost means to ascertain operation thereof,

said monitoring means comprising a combination of series and parallelrelays at the interconnection to said stator for determining a boostpower condition,

monitoring relay means operated responsive to the operation of saidseries and parallel relay combination to demonstrate the boost powercondition.

1. An induction motor supply system such as used for powering rotatinganode X-ray tubes, wherein the X-ray tube anode is either driven by themotor rotor or is the motor rotor, said power supply system comprising afirst solid-state power source for supplying normal power required fordriving the rotor of said motor at a first running speed, a secondsolidstate power source for supplying normal power required for drivingthe rotor of said motor at a second running speed, said second speedbeing higher than said first speed, boost means for increasing the powerto the motor for a predetermined period of time above the normal runningpower to accelerate the rotor while attaining said first and secondrunning speeds, means for decreasing said power to the normal runningpower after said predetermined period of time, and means for selectivelyconnecting the stator of said motor to either said first or said secondpower sources.
 2. The power supply system of claim 1 wherein boosttiming means are provided for automatically limiting the operating timeof said boost means.
 3. The power supply of claim 1 wherein means areprovided for monitoring said boost means to ascertain operation thereof.4. The power supply system of claim 1 wherein said first solid-statepower source means comprises control transformer means for coupling to apower line to provide low voltage at line frequency, means for couplingsaid line frequency signal from the secondary of said controltransformer to first solid-state phase shift means, said last-namedphase shift means for phase shifting said line frequency, means usingthe phase shifted line frequency to control a silicon-controlledrectifier bridge circuit so that the firing angles of the two siliconcontrolled rectifiers of the bridge circuit provide a boost power outputfrom said bridge circuit and a running power output from said bridgecircuit by varying the phase shift of said line frequency phase shiftnetwork means, and means for selectively connecting the output of saidsilicon controlled rectifier to the stator of said induction motor. 5.The power supply system of claim 4 including timing means for limitingthe time of the phase shift resulting in the boost power to therebyautomatically vary the phase shift after a first timer period.
 6. Aninduction motor power supply system such as used for rotating the anodeof X-ray tubes, wherein the X-ray tube anode is either driven by therotor of the induction motor or is the induction motor rotor, said powersupply system comprising a first solid state power source for supplyingnormal power required foR driving the rotor of said motor at a firstrunning speed, a second solid state power source for supplying normalpower for driving the rotor of said motor at a second running speed,said second speed being higher than said first speed, boost means forincreasing the power to the motor for a predetermined period of timeabove the normal running power to accelerate the motor while attainingsaid first and second running speeds, means for decreasing said power tothe normal running power after said predetermined period of time, meansfor selectively connecting the stator of said motor to either said firstor said second power sources, and braking means for braking said motorwhen switching from said second speed.
 7. The power supply system ofclaim 6 wherein braking timing means are provided for automaticallylimiting the operating time of said braking means.
 8. The power supplysystem of claim 6 wherein said braking means comprises a braking relay,means for operating said braking relay responsive to switching off saidsecond solid-state power source, means responsive to the operation ofsaid braking means for deaccelerating the speed of the anode from saidsecond speed to said first speed, and said last-named means comprisingmeans responsive to the operation of the braking relay for operatingsaid first solid-state power source at a boost power condition.
 9. Thepower supply means of claim 8 wherein means are provided automaticallytime limiting the operating period of said braking relay, whereby saidsecond power source is returned to the running power condition from theboost power condition at the end of a defined time period.
 10. Aninduction motor power supply system such as used for powering therotating anode of X-ray tubes, wherein the X-ray tube anode is eitherdriven by the motor rotor or is the motor rotor, said power supplysystem comprising a first solid-state power source for driving the rotorof said motor at a first running speed, a second solid-state powersource for driving the rotor of said motor at a second speed, saidsecond speed being higher than said first speed, boost means foraccelerating the rotor to said first and second speeds, means forselectively connecting the stator of said motor to either said first orsaid second power source, control transformer means for coupling to apower line to provide line frequency power, AC-to-DC power supply meanscoupled to the secondary of said control transformer for supplyingdirect current power, oscillator means powered from said direct currentpower for providing a signal having a frequency greater than the linefrequency, inverter means driven by said oscillator means to provide adriving power at a frequency higher than line frequency for driving thesaid rotor, and means for automatically restarting said inverter is saidinverter is extinguished.
 11. The power supply system of claim 10wherein said inverter comprises a silicon-controlled rectifier inverterhaving a first and a second SCR, said first and second SCRs normallyoperating individually, said oscillator means including inverter drivermeans having a pair of outputs, each of said outputs being individuallycoupled to one of the gates of said SCRs alternatively gating saidsilicon-controlled rectifiers, AC-to-DC converter means coupled to saidline power, the output of said AC-to-DC converter means being connectedacross said first and second SCRs, and said means for restarting saidinverter comprising restarting relay coil means connected across theoutput of said AC-to-DC converter means to keep said restarting relayenergized unless both SCRs are gated simultaneously, restarting normallyopen relay contact means in series with the output of said AC-to-DCconverter means for decoupling said AC-to-DC converter means from saidsilicon-controlled rectifier inverter in the event both of saidsilicon-controlled rectifiers are gated simultaneously, thereby removingpower from the silicon-controlled rectifier inverter means andautomatically reenergizing said restarting relay to reconnect saidinverter means to said AC-to-DC converter means.
 12. The induction motorpower supply system of claim 11 wherein said boost means comprises meansindividual to said second solid-state power source for providing aboosted power output from said second solid-state power source foraccelerating the anode so that it reaches the second speed in arelatively small time period.
 13. The power supply system of claim 12wherein the AC-to-DC converter means comprises a pair ofsilicon-controlled rectifiers, and wherein the boost means individual tosaid second solid-state power source comprises phase shift network meanscoupled to the secondary of said control transformer, the output of saidphase shift network being coupled to said AC-to-DC converter means fordetermining the firing angles of the silicon controlled rectifiers insaid AC-to-DC converter means and thereby determining the power outputfrom said AC-to-DC converter means.
 14. The power supply system of claim13 including timing means for automatically changing the phase shiftafter a first period of time to reduce the boosted power to normalrunning power.
 15. An induction motor power supply system such as usedfor rotating the anode of X-ray tubes, wherein the X-ray tube anode iseither driven by the motor rotor or is the motor rotor, said powersupply system comprising a first solid-state power source for drivingthe rotor of said motor at a first speed, a second solid-state powersource for driving the rotor of said motor at a second speed, saidsecond speed being higher than said first speed, boost means foraccelerating the rotor to said first and second speeds, secondsolid-state power source switching means for initiating the operation ofsaid second solid-state power source, means for selectively connectingthe stator of said motor to either said first or said second powersource comprising selection switching means operated responsive to theoperation of second solid-state switching means, and means responsive tothe operation of said selection switching means for switching thecoupling of the stator of the induction motor from the output of saidfirst solid-state power source to the output of said second solid-statepower source.
 16. The power supply system of claim 15 wherein saidselection switching means comprises a selection relay, and wherein saidsecond solid-state power source switching means comprises a secondsolid-state power source relay means, normally open contacts on saidsecond solid-state power source relay means operating to complete anoperating circuit for said selection relay.
 17. The power supply systemof claim 16 wherein split phase start capacitor means are provided forsaid induction motor, said split phase capacitor means comprising afirst and a second capacitor, means including contacts on said selectionrelay for connecting said first and second capacitors in parallel whensaid first power source is connected to the stator of said motor, meansincluding contacts on said switching relay for disconnecting said firstcapacitor responsive to said second solid-state power source beingcoupled to the stator of said induction motor.
 18. An induction motorsupply system such as used for powering X-ray tubes having rotatinganodes, wherein the X-ray tube anode is either driven by the motor rotoror is the motor rotor, said power supply system comprising a firstsolid-state power source for driving the motor of said rotor at a firstspeed, a second solid-state power source for driving the rotor of saidmotor at a second speed, said second speed being higher than said firstrunning speed, boost means for increasing the power to the motor abovethe normal runNing power to accelerate the rotor while obtaining thefirst and second running speeds, means for selectively connecting thestator of said motor to either said first or said second power sources,and means for monitoring said boost means to ascertain operationthereof, said monitoring means comprising a combination of series andparallel relays at the interconnection to said stator for determining aboost power condition, monitoring relay means operated responsive to theoperation of said series and parallel relay combination to demonstratethe boost power condition.